The poisonous dorsal spines on the back large pink colored Reef Stonefish (Synanceia verrucosa) sitting on the top of the famous Steve Bommie's dive site within the Great Barrier reef in North Queensland, Australia.
These massively venomous, but docile, ambush hunters have hurt people who have accidentally stepped on their poisonous spines located on their back. Their camouflage is almost perfect, and they are willing to sit totally still even when disturbed to maintain the illusion. The raised spines here are only raised when a true threat is felt (such as someone accidentally stepping on the fish.)